Brake assembly



Jan. 17, 1956 w. H. DU BOIS BRAKE ASSEMBLY 2 Sheets-Sheet 1 Filed Nov.1, 1950 I N V EN TtOR. W/LL/A/V 0050/5 jaw Jan. 17, 1956 w. H. DU BOIS2,731,312

BRAKE ASSEMBLY Filed Nov. 1. 1950 2 Sheets-Sheet 2 IN V EN TOR.

Mam/VA! 0060145 BRAKE ASSEMBLY William H. Du Bois, South Bend, Ind,assignor to Bendix Aviation Corporation, South Bend, 1nd,, a corporation of Delaware Application November 1, 1950, Serial No. 193,455

Claims. (Cl. 309--3) The present invention relates to brakes and moreparticularly to aircraft brakes of the disc type. The method for makingthe present invention is covered by my copending application Serial No.525,749, filed August 1, 1955.

The conventional disc brake hydraulic motor or actuator comprises ametal carrier which has machined therein a piston chamber or bore whichmay assume any regular or irregular shape as for instance that of anincomplete annulus, a complete annulus, a cylinder, or some odd shapesuch as that of a heart or kidney. In producing these various chambers,it has been necessary to machine the side walls with suitable tools toobtain the desired shape and size, and degree of wall smooth ness. For achamber shape of an incomplete annulus, the machining operation istedious and expensive. It is, therefore, an important object of thisinvention to provide a hydraulic brake actuator in which it is notnecessary to machine the piston chamber. It is a further object toprovide a method for producing this actuator.

In accomplishing the product of the present invention, a rough castingis first made and has formed therein an oversized piston chamberhereinafter characterized as a cavity. Certain of the outer fastening orjoining sur faces of the casting are then machined, after which a moldinsert having the shape and size of the actuator piston is inserted intothe cavity. Next, either a thermosetting or a thermoplastic material isinjected into the spaces between the insert and the cavity walls,whereby a lining is effectively molded to the walls of the cavity. Afterthe injected material sets, the insert is withdrawn leavinga pistonchamber which is ready, without any machining, to reciprocably receive apiston. Thus, it is seen that a hydraulic brake actuator may be producedwithout following conventional machining steps. The lining for thecavity is held in place by virtue of the rough cavity surfaces resultingfrom the casting operation. However, by forming the cavity and liner ina certain manner as will heinafter be described, no holding means isnecessary for keeping the liner in place, and it is, therefore, anotherobject of this invention to provide a novel construction for retaining aplastic lining in a piston cavity.

The embodiment of the present invention herein disclosed is quitesimilar to that of DuBois application Serial No. 150,177 filed March 17,1950.

In the drawings:

nited States Patent 0 Figure 1 is a side elevation of an embodiment ofthe present invention with certain parts thereof being shown in section;

Figure 2 is an axial section taken substantially on section line 2--2 ofFigure l and Figure 3 is a sectional illustration of a device used infabricating the hydraulic actuator used in Figures 1 and 2.

Referring to the drawings, and more particularly to Figure 2, a wheeland brake assembly ltl is shown as being supported by an axle l2projecting laterally from the lower extremity of strut M. The wheel 16is pro- 2,731,312 Patented Jan. 17, 1956 vided with a brake cavity 18which receives a disc brake generally indicated by reference numeral 20.This brake Z0 is composed of a plurality of interleaved rotatable andnon-rotatable friction discs or members 22 and 24, respectively.Rotatable discs 22 are rotatable with wheel 16 and are axially movablewith respect to the latter by means of a plurality of axially extending,circumferentially spaced driving keys 26 which are suitably secured nearthe outer periphery of brake cavity 18.

A carrier or supporting member 28, which serves as the torque-takingmember of the brake, is provided with a central opening 30 whichreceives the axle 12. A reinforcing flange 32 on the axle 12 provides aconvenient attaching means for securing carrier 28 in place. A pluralityof axially extending, circumferentially spaced bolts 34 are secured nearthe outer periphery of carrier 28, and rigidly support a backing plateor reaction member 36 adjacent one end of the stack of friction discs 22and 24. A plurality of sleeve type keys 38 are received on bolts 34, andare adapted to be slidingly engaged by notches formed in non-rotatablediscs 24 whereby said discs 24 are held against rotation but permittedto move axially. A pressure plate 40 is also keyed to keys 38 and islocated at the end of the friction disc 22, 24 stack opposite backingmember 36. As is illustrated in Figure 2, the discs 22 and 24 may becompressed into frictional engagement by forcing pressure plate dilltoward the backing plate 36.

Referring now to Figures 1 to 3, the carrier 28 is provided with apiston chamber 42 which reciprocably receives a piston 44. This piston44 is arranged to act on pressure plate ill, and is provided on its headend with a rubber or the like seal 46. The chamber 48 ahead of the seal46 is connected by a suitable means to a controllable source of pressurefluid which, through the intermediary of chamber 43, forces piston 44outwardly against pressure plate 40.

As is noted in the sectional views, the piston chamber 42 is defined bydifferent material than that of carrier 28. Actually, it is preferred tocast the carrier 28, in the conventional manner, of a. suitable metal,the cast form of the carrier providing an oversized piston cavity 5twhich is defined by opposite rough cast walls and a bottom.

The present invention is particularly useful in connection withhydraulic actuator constructions, such as the one herein disclosed,which has the shape of an incomplete annulus. Morewill be said laterregarding the particular value of the present invention as embodied inthis actuator construction, but it is suiiicierit to recognize at thispoint that the general shape of the cavity St is that of an incompleteannulus.

The rough casting, of carrier 28 is machined to provide smooth,substantiallyparallel surfaces 52. and 54, and the pilot hole 30 is alsoreamed or broached for a purpose to be explained hereafter. The pistonchamber 4-2 is defined by a liner 5s preferably formed of athermoplastic or thermosetting material molded into the rough cavity 50.It will be obvious that the rough, unfinished surfaces of cavity 50serve the useful purpose of providing irregularities for securing theliner 56 in place inasmuch as the contiguous portions of liner 56intimately follow the irregularities to become in effect keyed thereto.Actually, if desired, small variations or irregularities may be cut orscratched in cavity 50 for this same purpose. it being obvious that itis the roughened surfaces which perform the function of securing theliner 5a in place.

One principal obiection in producing all-rnetal carriers withpiston-receiving bores is the cost involved in machining the interiorsof the chambers to the desired sizes, shapes, and degrees of smoothness.By lining the walls of a cast cavity with a plastic material of eitherthe thermoplastic or thermosetting type, this costly machining iseliminated, and a piston chamber of'the proper size and shape isproduced by essentially only two simple operationscasting the roughcarrier 28 and molding a liner 56 in'position.

Referring to Figure 1 of the drawings, it is seen that the hydraulicactuator 'is less than a complete annulus. While it is particularlyadvantageous to utilize the pres ent invention in forming such anactuator, it is to be understood that the basic principles of thisinvention may be utilized to fabricate other actuators.

The conventional method of forming an incomplete annular chamber is tomill the sides thereof by carefully and tediously following the desiredcontour. This milling is obviously time consuming and costly, thereforenot conducive to economical production. By molding a liner in place, asheretofore explained, the economy and quantity of production may bestepped up considerably.

In forming the liner 56, a mold is used which comprises essentially aplaten 58 and a mold clamp 60. The platen 53 carries a pilot stub 62which is snugly received in carrier opening 31 andclamp 60 has extendingtherefrom a mold insert 64 having a size and shape of the pistonnormally received in chamber 42. The platen 58 is fitted as shownagainst carrier surface 52, and clamp 60 is centered with respect to theplaten 53 and also carrier 28 by means of an opening 66 which receivesstub 62. The mold insert 64 is thereby positioned within rough cavity 48leaving side and bottom spaces to be occupied by the liner. The platen58 and clamp 69 are clamped together by a suitable means such as the nutand bolt combination 68. Preferably, molten or fluid plastic material isinjected into the liner spaces and allowed to set whereby the moldinsert may be removed leaving a piston chamber 42 which is ready toreceive a piston. Figure 3 illustrates one method for injecting thefluid plastic, which is to force the plastic through multipleperforations 70 in the carrier 23 which connect the liner spaces withpassages 72 in platen 58. With certain types of lining material, it isnecessary to heat the molding fixture to a predetermined temperaturebefore performing the molding operation in order to achieve the desiredintimate fit between linear and cavity.

The brake assembly operates by introducing liquid under pressure intochamber 48, which forces piston 44 outwardly to compress the frictiondiscs 22 and 24 against backing plate 36. It will be noted that duringthis action, the liquid pressure in chamber 48 acts against the bottomsurface of liner 56, tending to retain the liner 56 in its socket orcavity 50. Thus, double retaining means are available to maintain theliner 56 in place, these means being the rough surfaces of cavity 50 andthe liquid pressure in chamber 48. With this particular linerarrangement, the liner becomes a definite cooperative part of the brakeassembly.

The brake assembly is released by relieving the pressure in chamber 48whereupon piston 44 and pressure plate 40 are forced to separate frombacking plate 36 by means of return springs (not shown).

The brake of this invention, as explained above, is economical andreliable, and the method by which it is produced is simple, economical,and relatively expeditious.

Although only one embodiment of the invention has been illustrated anddescribed, various changes in the form and relative arrangements of theparts may be made to suit requirements.

I claim:

1. An annular supporting member adapted for use with a friction brakemechanism, said member including a semi-annular rough cavity providedwith a bottom portion, a plastic liner intimately fitted to the walls ofsaid cavity and providing a semi-annular chamber, the rough contour ofthe walls of said cavity tending to secure said liner in place, and apiston reciprocably received in said chamber, said chamber and saidpiston having uniform radial dimensions throughout their arcuatelengths.

2. in a disc brake mechanism, an annular supporting member comprising arough cavity provided with a bottom portion, a liner composed of aplastic material intimately fitted to the walls of said cavity andproviding a chamber having smooth sides, the intimate contact betweenthe rough cavity walls and the liner providing the means for securingsaid liner in place, and a piston reciprocably received in said chamber.

3. An annular supporting member adaptive for use in a disc brakemechanism, said member including a rough cavity rectangular in sectionaloutline, a plastic liner intimately fitted to the walls of said cavityand providing a power fluid receiving chamber, the rough contour of thewalls of said cavity tending to secure said liner in place, and a motorpiston reciprocably received in said chamber, said chamber and saidpiston having substantially uniform radial dimensions throughout theirarcuate lengths.

4. In a circular disc brake, an annular supporting memher, an arcuatecavity formed in said supporting member and being provided withroughened walls, a liner composed of plastic material anchored to theroughened walls of said cavity and providing a chamber having smoothsides, said sides being located throughout their actual length at apredetermined radial distance from the center of said supporting member,said liner being secured in place by intimate contact between the roughcavity walls and the liner, and a piston reciprocably received in saidchamber and subjected to fluid pressure, said fluid also bearing againstthe bottom of said liner tending to solidly retain said liner in thecavity.

5. In a disc brake including an annular supporting member having asemi-annular cavity concentrically formed therein, said cavity having abottom and roughened walls, a liner formed of plastic materialintimately fitted with said bottom and walls, a piston reciprocablyreceived in said chamber and subjected to fluid pressure, said fluidalso bearing against the bottom of said liner tending to solidly retainsaid liner in the cavity.

References Cited in thefile of this patent UNITED STATES PATENTS1,584,413 Warner May 11, 1926 1,621,858 Sherwood Mar. 22, 1927 1,919,455Wilson July 25, 1933 2,132,978 Stewart Oct. 11, 1938 2,279,671 Ford Apr.14, 1942 2,304,589 Nickerson Dec. 8, 1942 2,407,559 Krotz Sept. 10, 19462,423,881 DuBois July 15, 1947 FOREIGN PATENTS 113,084 Sweden Jan. 30,1945

